This invention relates to apparatus for leveling boom-carried containers which support aerial workmen, such as telephone linemen and the like, and pertains in particular to arrangements in which leveling is achieved hydraulically.
Boom-carried containers are generally called baskets and must be stable in order to protect the occupants from being dumped out as the boom is manipulated. That is, as the boom moves, the basket must constantly remain in a level position. Typically, leveling is achieved through a hydraulic system.
Historically, hydraulic systems have been either costly or relatively insensitive and unstable. For example, where the hydraulic system is controlled by a pendulum, sudden stops and starts of the boom cause the pendulum to osciliate thereby introducing vascilations into the system. If the vascilations are not damped, the system will over-control and the basket will swing. Attempts to prevent such oscilations have heretofore generally proved to be costly, complicated or both.
Accordingly, the object of this invention is to achieve stable leveling control in a simple and reliable structure.